s1_read_last_two_bytes_of_a_mbr_backup_file() {

    local file_path=$1

    local last_bytes=$(tail -c 2 "$file_path" | od -A n -t x1 | tr -d ' \n')

    if [ "$last_bytes" = "55aa" ];then

        echo "YES"

    else

        echo "NO"

    fi

}



s2_read_mbr_partition_table_info() {

    for i in {0..3}; do

        offset=$((446 + i * 16))

        start_sector=$(dd if="$1" bs=1 skip=$((offset + 8)) count=4 2>/dev/null | od -t u4 -An | tr -d ' \n')

        if ! [[ $start_sector =~ ^[0-9]+$ ]];then

            continue

        fi

        if [ "$start_sector" -eq 0 ];then

            continue

        fi

        size_sector=$(dd if="$1" bs=1 skip=$((offset + 12)) count=4 2>/dev/null | od -t u4 -An | tr -d ' \n')

        end_sector=$((start_sector + size_sector - 1))

        echo "$start_sector $end_sector"

    done

}



s3_parse_partition_info(){

    fdisk_output=$(cat)

    disk_size_bytes=$(echo "$fdisk_output" | grep "Disk /dev/vda:" | awk '{print $5}')

    disk_size_sectors=$(echo "$fdisk_output" | grep "Disk /dev/vda:" | awk '{print $7}')

    physical_sector_size=$(echo "$fdisk_output" | grep "Sector size" | awk '{print $4}')

    first_partition_start_sector=$(echo "$fdisk_output" | grep "/dev/vda1" | awk '{print $3}')

    first_partition_end_sector=$(echo "$fdisk_output" | grep "/dev/vda1" | awk '{print $4}')

    first_partition_type=$(echo "$fdisk_output" | grep "/dev/vda1" | awk '{print $8}')

    echo "disk size in bytes:$disk_size_bytes"

    echo "disk size in sectors:$disk_size_sectors"

    echo "physical sector size in bytes:$physical_sector_size"

    echo "first partition start sector id:$first_partition_start_sector"

    echo "first partition end sector id:$first_partition_end_sector"

    echo "first partition type:$first_partition_type"

}



s4_run_passwd_as_plain_user_and_get_status() {

    oversleeping_path=$(which oversleeping)

    chown root "$oversleeping_path"

    chmod 4755 "$oversleeping_path"

    oversleeping &

    ps -o uid,euid,ruid -C oversleeping | awk 'NR>1 {print $1","$2","$3}'

}



s5_add_a_scheduled_task() {

    touch $HOME/test_crontab;

    echo "*/5 * * * * date +\%Y\%m\%d_\%H\%M\%S >> $HOME/test_crontab" | crontab -

} 
